1. Field of the Invention
This invention relates generally to spinal fixation devices, and more particularly to a wrench for facilitating the mounting and tightening of a nut onto a bolt secured in a bone of a person's spine.
2. Description of the Prior Art
During the application of spinal fixation devices to the spine of a person, there is often some difficulty in the assembly of a nut onto a bolt which is deeply implanted in the person's spine, particularly in the pedicle. The surgical exposure to a patient's lumbar spine is very deep, meaning that there is typically four to five inches of skin and muscle tissue against which instruments have to be used. It is often necessary to attach nuts to bolts that are screwed into the pedicle. Because the nuts are comparatively small, and the depth in tissue is significant, it is usually difficult to properly align a nut with the thread on the bolt to get the nut started. Another problem after the nut has been mounted on the bolt, is to avoid tightening of the nut so much as to cause the bolt to turn in the bone, which would result either in advancing the bolt farther into the bone than is intended, or the strippage of the bone screw threads of the bolt in the patient's spine pedicle. The present invention is directed to avoiding these problems.